The present invention relates to a method and apparatus for controlling activity of developing solution against oxidation by using a test piece for use in an automatic developer.
In a conventional automatic photographic film developer, the activity of the developing solution which is fatigued or lowered by the film blackening, has been maintained at the proper value in some methods as follows:
(a) The replenishment of a supplementary solution against the blackening is carried out depending on a developed area of the photographic film and a predetermined blackening rate.
(b) The supplementary solution is supplemented depending on a blackened area measured on the photographic film.
(c) The supplementary solution is replenished in a certain period of time corresponding to the measured length of the photographic film to be processed, whose predetermined unit length requires the supplement of a certain volume of the supplementary solution.
The developing solution is also fatigued by oxidation by means of the air, and the like. The degree of the oxidation of the developing solution is different between during and in the absence of the operation of the automatic developer. Hence, in general, the amount of the supplementary solution per unit period of time should be varied during and in the absence of the operation of the developer.
However, while such an activity control of the developing solution is continued, the control errors are accumulated. Accordingly, the activity of the developing solution must be further controlled, for example, twice a day by using a test piece.
In a conventional activity control method of the developing solution against the oxidation, the test pieces exposed with predetermined light and shade and are processed in the standard developing solution and the developing solution whose activity is to be controlled, separately. Then the densities at the predetermined light and shade points of the developed test piece processed in the developing solution to be controlled are compared with those of the test piece processed in the standard developing solution, with the naked eye or a densitometer. Then, depending on the difference of these densities, the supplementary solution is added to the developing solution to be controlled on the basis of the operator's experiences and skill, in order to restore the activity of the developing solution.
In this method, however, the determination of the exact amount of the supplementary solution corresponding to the density difference of the two test pieces is very difficult. Accordingly, in practice, the supplementary solution is usually added in a somewhat smaller amount in a manual manner, and then the activity of the developing solution is measured by using the test piece. Then, the supplementary solution is added to the developing solution depending on the measured result, thereby obtaining a proper activity. However, this operation is very troublesome and involves a lot of time.